(1) Field of the Invention
This application pertains to valves and particularly pertains to valves having a valve member which is mounted in a body and rotated between open and closed positions.
(2) Background Information
Quite a number of valves have been developed which utilize resilient sealing materials for sealing between internal valve parts and metal valves and metal seats which rub on each other through the full arc as the valve member is rotated between open and closed positions. The resilient sealing materials often deteriorate rapidly as affected by high temperatures, chemical action and possibly erosion to a condition in which they no longer seal internal valve parts to one another. After metal valves and seats rub on each other through full turning arcs numerous times, metal sealing surfaces tend to gall ruining one or both of the sealing surfaces for sealing engagement with each other resulting in valve leakage. Particles of grit on metal sealing surfaces also may damage these surfaces to no longer sealingly engage. To have a reliable seal, the metal-to-metal valve and seats should have large areas for sealing engagement and should sealingly engage throughout the entire contacting area.
A mathematical analysis was made of arcs of circles, involutes, archimedean spirals, logarithmic spirals, epicycloids and hypocycloids to determine the most desirable curved surface for metal sealing surfaces. The involute of a circle was found to have all the required characteristics. The location of points on the involute curve was calculated and it was found there were a number of existing manufacturing processes which could be used to form involute curves on metal valve members and in metal valve bodies.